U.S. patent number 6,555,593 [Application Number 09/240,020] was granted by the patent office on 2003-04-29 for photopolymerization compositions including maleimides and processes for using the same.
This patent grant is currently assigned to Albemarle Corporation. Invention is credited to Shan Christopher Clark, Charles E. Hoyle, E. Sonny Jonsson, Christopher W. Miller, Rajamani Nagarajan, Liying Shao.
United States Patent |
6,555,593 |
Hoyle , et al. |
April 29, 2003 |
**Please see images for:
( Certificate of Correction ) ** |
Photopolymerization compositions including maleimides and processes
for using the same
Abstract
Photopolymerization compositions which include maleimides and
processes using the same are disclosed. Polymerization of
compositions which include maleimides in combination with a
benzophenone compound/hydrogen atom donor sensitizer system may be
activated by irradiating the composition with radiation.
Inventors: |
Hoyle; Charles E. (Hattiesburg,
MS), Nagarajan; Rajamani (Oceans Springs, MS), Miller;
Christopher W. (Hattiesburg, MS), Clark; Shan
Christopher (Hattiesburg, MS), Jonsson; E. Sonny
(Stockholm, SE), Shao; Liying (Queensland,
AU) |
Assignee: |
Albemarle Corporation (Baton
Rouge, LA)
|
Family
ID: |
22111727 |
Appl.
No.: |
09/240,020 |
Filed: |
January 29, 1999 |
Current U.S.
Class: |
522/63; 522/166;
522/178; 522/181; 522/33; 522/46; 522/182; 522/167 |
Current CPC
Class: |
G03F
7/031 (20130101); C08F 2/50 (20130101) |
Current International
Class: |
G03F
7/031 (20060101); C08F 002/50 (); C08F 002/48 ();
C08F 002/46 () |
Field of
Search: |
;522/167,166,63,178,181,182,33,46 |
References Cited
[Referenced By]
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|
Primary Examiner: Seidleck; James J.
Assistant Examiner: McClendon; Sanza L.
Attorney, Agent or Firm: Alston & Bird LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to commonly owned copending Provisional
Application Ser. No. 60/073,100, filed Jan. 30, 1998, incorporated
herein by reference in its entirety, and claims the benefit of its
earlier filing date under 35 U.S.C. 119(e).
Claims
That which is claimed is:
1. A photopolymerizable composition comprising at least one
photopolymerizable compound having at least one ethylenically
unsaturated double bond, at least one maleimide compound capable of
initiating photopolymerization of said ethylenically unsaturated
compound in an amount of about 0.01 to about 2 mole percent, and at
least one photoactive benzophenone compound which is a sensitizer
capable of sensitizing initiation of the ethylenically unsaturated
compound by said maleimide.
2. The composition of claim 1, wherein said at least one maleimide
compound is selected from the group consisting of alkyl maleimides,
functionalized aliphatic maleimides, aromatic maleimides,
maleimide, maleic anhydride, and mixtures thereof.
3. The composition of claim 2, wherein said maleimide compound
comprises an alkyl maleimide of the formula ##STR17##
wherein: each R.sub.1 and R.sub.2 is independently selected from
the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused substituted or unsubstituted saturated or unsaturated five or
six membered cyclic hydrocarbon or heterocyclic ring system; and R
is straight chain, branched or cyclic C1-C10 alkyl, optionally
substituted with one or more C1-C4 alkyl.
4. The composition of claim 3, wherein said alkyl maleimide is
selected form the group consisting of methyl maleimide, hexyl
maleimide, cyclohexyl maleimide, and mixtures thereof.
5. The composition of claim 2, wherein said functionalized
aliphatic maleimide comprises a compound of the formula:
##STR18##
wherein: (a) each R.sub.1 and R.sub.2 is independently selected
from the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused substituted or unsubstituted saturated or unsaturated five or
six membered cyclic hydrocarbon or heterocyclic ring system; (b)
R.sub.4 is linear or branched C1 to C10 alkyl, heteroatom, or
silicon --SiH.sub.2 --; and (c1) when R.sub.4 is C1 to C10 alkyl,
FG is a functional group selected from the group consisting of
--OR.sub.3, --SR.sub.3, --SiH.sub.2 R.sub.3
,--OC(O)N(R.sub.3).sub.2, --OC(O)C(.dbd.CHR.sub.3)R.sub.3,
--OC(O)R.sub.3, --C(O)R.sub.3, --N(R.sub.3).sub.2, --C(O)OR.sub.3,
--NCO, --C(O)N(R.sub.3).sub.2, --OC(O)OR.sub.3, --CN, halogen,
--CH.sub.2 N-aryl-FG', --CH.sub.2 N-aryl-R.sub.3 -FG', sulfonic
acid, quaternary ammonium, and salts thereof, in which each R.sub.3
is selected from the group consisting of hydrogen, alkyl, aryl,
cycloalkyl, arylalkyl, and alkylaryl, and in which FG' is selected
from the group consisting of --OR.sub.3, --SR.sub.3, --SiH.sub.2
R.sub.3, --OC(O)N(R.sub.3).sub.2, --OC(O)C(.dbd.CHR.sub.3)R.sub.3,
--OC(O)R.sub.3, --C(O)R.sub.3, --N(R.sub.3).sub.2, --C(O)OR.sub.3,
--NCO, --C(O)N(R.sub.3).sub.2, --OC(O)OR.sub.3, --CN, halogen,
sulfonic acid, and quaternary ammonium, or (c2) when R.sub.4 is a
heteroatom or silicon --SiH.sub.2 --, FG is selected from the group
consisting of hydrogen, alkyl, aryl, cycloalkyl, alkylaryl,
arylalkyl, alkyl-FG", and aryl-FG", wherein FG" is the same as FG'
as defined in (c1) above, or (c3) FG is a functional group as
defined in (c1) in combination with a spacer group linking said
maleimide unit with at least one other maleimide unit to form a di-
or multifunctional maleimide compound.
6. The composition of claim 5, wherein said functionalized
aliphatic maleimide is selected from the group consisting,of
hydroxy methylmaleimide, hydroxy ethylmaleimide, triethylene glycol
biscarbonate bisethylmaleimide, 2-ethylcarbonate ethylmaleimide,
2-isopropyl urethane ethylmaleimide, 2-acryloyl ethylmaleimide,
acetoxy ethyl maleimide, isophorone bisurethane bisethylmaleimide,
bisethylmaleimide carbonate, 4,9-dioxa-1,12 dodecane bismaleimide,
bispropyl maleimide, dodecane N,N'-bismaleimide, and mixtures
thereof.
7. The composition of claim 2, wherein said aromatic maleimide
comprises a compound of the formula ##STR19##
wherein: each of R.sub.5, R.sub.6, R.sub.7, R.sub.8, and R.sub.9 is
independently selected from the group consisting of H, CX.sub.3,
COOR.sub.12, COR.sub.12, OR.sub.12, CN, SR.sub.12,
N(R.sub.12).sub.2, R.sub.13, X, and MI; R.sub.10 and R.sub.11 each
is independently selected from the group consisting of H, C1 to C10
alkyl, cycloalkyl, aryl, alkoxy, and halogen, or R.sub.1 and
R.sub.2 together form a fused substituted or unsubstituted
saturated or unsaturated five or six membered cyclic hydrocarbon or
heterocyclic ring system; X is halide; R.sub.12 is selected from
the group consisting of H, lower alkyl, cycloalkyl, and aryl;
R.sub.13 is selected from the group consisting of lower alkyl,
cycloalkyl, and aryl, or R.sub.13 is a spacer group connecting at
least two compounds of the above formula to form a di- or
multi-functional maleimide; and MI is ##STR20## wherein R.sub.10
and R.sub.11 are as defined above.
8. The composition of claim 7, wherein said aromatic maleimide is
selected from the group consisting of phenyl maleimide,
N-(2-CF.sub.3 -phenyl)maleimide, N-(2-t-butylphenyl)maleimide,
N-(2-CF.sub.3 -phenyl)methylmaleimide,
N-(2,4,6-isopropyl-3-maloimide phenyl)maleimide,
N-(2-iodophenyl)maleimide, N-(2-bromo-3,5-CF.sub.3 -phenyl)
maleimide, di(4-maleimido phenyl)methane, N-(2-chlorophenyl)
maleimide, N-(2-bromophenyl) maleimide, N-(2-fluorophenyl)
maleimide, N-(4-CF.sub.3 -phenyl) maleimide,
di(3,5-diethyl-4-maleimidophenyl)methane, and mixtures thereof.
9. A photopolymerizable composition comprising at least one
photopolymerizable compound having at least one ethylenically
unsaturated double bond, at least one maleimide compound capable of
initiating photopolymerization of said ethylenically unsaturated
compound of the formula ##STR21##
wherein each R.sub.1 and R.sub.2 is independently selected from the
group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl, aryl,
alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a fused
substituted or unsubstituted saturated or unsaturated five or six
membered cyclic hydrocarbon or heterocyclic ring system, and at
least one photoactive compound without a maleimide functionality
which is a sensitizer capable of sensitizing initiation of the
ethylenically unsaturated compound by said maleimide.
10. A photopolymnerizable composition comprising at least one
photopolymerizable compound having at least one ethylenically
unsaturated double bond at least one maleic anhydride capable of
initiating photopolymeration of said ethylenically unsaturated
compound of the formula ##STR22##
wherein each R.sub.1 and R.sub.2 is independently selected from the
group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl, aryl,
alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a fused
substituted or unsubstituted saturated or unsaturated five or six
membered cyclic hydrocarbon or heterocyclic ring system, and at
least one photoactive compound without a maleimide functionality
which is a sensitizer capable of sensitizing initiation of the
ethylenically unsaturated compound by said maleic anhydride.
11. The composition of claim 1, wherein said benzophenone compound
comprises a compound of the formula ##STR23##
wherein: B is (H,H), --CH.sub.2 --, --S--, --O--, --CO--,
--NR.sub.15 --, or a bond bridging the two aromatic rings; each
R.sub.14 is independently selected from the group consisting of
hydrogen, alkyl, cycloalkyl, alkoxy, aryl, alkylaryl, arylalkyl,
halogen, trihaloalkyl, --CN, --NO.sub.2 , --C(O)OR.sub.15,
--C(O)R.sub.15, --OR.sub.15, --N(R.sub.15).sub.2,
--OC(O)CR.sub.15.dbd.CHR.sub.15, R.sub.16, --OR.sub.16, --R.sub.17
--OC(O)CR.sub.15.dbd.CHR.sub.15, polymnerizable moieties, and
oligomeric and polymeric moieties; R.sub.15 is selected from the
group consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl,
and alkylaryl; R.sub.16 is one or more saturated or unsaturated
five or six membered hydrocarbon or heterocyclic ring system,
optionally substituted with one or more alkyl, cycloalkyl, or
halogen; and R.sub.17 is selected from the group consisting of
alkyl, aryl, cycloalkyl, arylalkyl, and alkylaryl.
12. The composition of claim 1, wherein said benzophenone compound
is selected from the group consisting benzophenone, thioxanthone,
isopropylthioxanthone, chloroxanthone, 4-morpholinobenzophenone,
4,4'-diphenoxybenzophenone, methyl o-benzoylbenzoate,
1-methyl-2-(2-ethylhexyloxy)thioxanthone,
4,4'-di-(4-isopropylphenoxy)benzophenone, acrylic acid
4-benzoylphenyl ester, 4,4'-diphenylbenzophenone,
4-phenylbenzophenone, and mixtures thereof.
13. The composition of claim 1, wherein said at least one
photopolymerizable compound is selected from the group consisting
of monomers and oligomers derived from acrylic and methacrylic
acid, optionally dispersed or dissolved in a solvent that is
copolymerizable therewith.
14. The composition of claim 13, wherein said photopolymerizable
compound is selected from the group consisting of methyl acrylate,
ethyl acrylate, n- or tert-butylacrylate, isooctyl acrylate, methyl
methacrylate, ethylmethacrylate, 2-ethylhexyl methacrylate,
butylacrylate, isobutyl methacrylate, hydroxy acrylates, glycol
acrylates, allyl acrylates, epoxy acrylates, aminoplast acrylates,
acrylated epoxides, acrylated polyesters, acrylated polyurethanes,
and mixtures thereof.
15. The composition of claim 1, wherein said composition further
comprises at least one hydrogen atom donor compound.
16. The composition of claim 15, wherein said hydrogen atom donor
compound comprises a tertiary amine.
17. The composition of claim 1, wherein said photopolymerizable
compound comprises a hydrogen atom donor molecular component.
18. A method of polymerizing a polymerizable compound having at
least one ethylenically unsaturated double bond, comprising
exposing said compound to radiation in the presence of at least one
maleimide compound in an amount of about 0.01 to about 2 mole
percent and at least one photoactive benzophenone compound, wherein
said maleimide initiates photopolymerization of said ethylenically
unsaturated compound and wherein said photoactive benzophenone
compound sensitizes initiation of the ethylenically unsaturated
compound by said maleimide.
19. The method of claim 18, wherein said at least one maleimide
compound is selected from the group consisting of alkyl maleimides,
functionalized aliphatic maleimides, aromatic maleimides,
maleimide, maleic anhydride, and mixtures thereof.
20. The method of claim 19, wherein said maleimide compound
comprises an alkyl maleimide of the formula ##STR24##
wherein: each R.sub.1 and R.sub.2 is independently selected from
the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused substituted or unsubstituted saturated or unsaturated five or
six membered cyclic hydrocarbon or heterocyclic ring system; and R
is straight chain, branched or cyclic C1-C10 alkyl, optionally
substituted with one or more C1-C4 alkyl.
21. The method of claim 20, wherein said alkyl maleimide is
selected form the group consisting of methyl maleimide, hexyl
maleimide, cyclohexyl maleimide, and mixtures thereof.
22. The method of claim 19, wherein said functionalized aliphatic
maleimide comprises a compound of the formula: ##STR25##
wherein: (a) each R.sub.1 and R.sub.2 is independently selected
from the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused substituted or unsubstituted saturated or unsaturated five or
six membered cyclic hydrocarbon or heterocyclic ring system; (b)
R.sub.4 is linear or branched C1 to C10 alkyl, heteroatom, or
silicon --SiH.sub.2 --; and (c1) when R.sub.4 is C1 to C10 alkyl,
FG is a functional group selected from the group consisting of
--OR.sub.3, --SR.sub.3, --SiH.sub.2
R.sub.3,--OC(O)N(R.sub.3).sub.2, --OC(O)C(.dbd.CHR.sub.3)R.sub.3,
--OC(O)R.sub.3, --C(O)R.sub.3, --N(R.sub.3).sub.2, --C(O)OR.sub.3,
--NCO, --C(O)N(R.sub.3).sub.2, --OC(O)OR.sub.3, --CN, halogen,
--CH.sub.2 N-aryl-FG', --CH.sub.2 N-aryl-R.sub.3 --FG', sulfonic
acid, quaternary ammonium, and salts thereof, in which each R.sub.3
is selected from the group consisting of hydrogen, alkyl, aryl,
cycloalkyl, arylalkyl, and alkylaryl, and in which FG' is selected
from the group consisting of --OR.sub.3, --SR.sub.3, --SiH.sub.2
R.sub.3, --OC(O)N(R.sub.3).sub.2, --OC(O)C(.dbd.CHR.sub.3)R.sub.3,
--OC(O)R.sub.3, --C(O)R.sub.3, --N(R.sub.3).sub.2, --C(O)OR.sub.3,
--NCO, --C(O)N(R.sub.3).sub.2, --OC(O)OR.sub.3, --CN, halogen,
sulfonic acid, and quaternary ammonium, or (c2) when R.sub.4 is a
heteroatom or silicon --SiH.sub.2 --, FG is selected from the group
consisting of hydrogen, alkyl, aryl, cycloalkyl, alkylaryl,
arylalkyl, alkyl-FG", and aryl-FG", wherein FG" is the same as FG'
as defined in (c1) above, or (c3) FG is a functional group as
defined in (c1) in combination with a spacer group linking said
maleimide unit with at least one other maleimide unit to form a di-
or multifunctional maleimide compound.
23. The method of claim 22, wherein said functionalized aliphatic
maleimide is selected from the group consisting of hydroxy
methylmaleimide, hydroxy ethylmaleimide, triethylene glycol
biscarbonate bisethylmaleimide, 2-ethylcarbonate ethylmaleimide,
2-isopropyl urethane ethylmaleimide, 2-acryloyl ethylmaleimide,
acetoxy ethyl maleimide, isophorone bisurethane bisethylmaleimide,
bisethylmaleimide carbonate, 4,9-dioxa-1,12 dodecane bismaleimide,
bispropyl maleimide, dodecane N,N'-bismaleimide, and mixtures
thereof.
24. The method of claim 19, wherein said aromatic maleimide
comprises a compound of the formula ##STR26##
wherein: each of R.sub.5, R.sub.6, R.sub.7, R.sub.8, and R.sub.9 is
independently selected from the group consisting of H, CX.sub.3,
COOR.sub.12, COR.sub.12, OR.sub.12, CN, SR.sub.12,
N(R.sub.12).sub.2, R.sub.13, X, and MI; R.sub.10 and R.sub.11 each
is independently selected from the group consisting of H, C1 to C10
alkyl, cycloalkyl, aryl, alkoxy, and halogen, or R.sub.1 and
R.sub.2 together form a fused substituted or unsubstituted
saturated or unsaturated five or six membered cyclic hydrocarbon or
heterocyclic ring system; X is halide; R.sub.12 is selected from
the group consisting of H, lower alkyl, cycloalkyl, and aryl;
R.sub.13 is selected from the group consisting of lower alkyl,
cycloalkyl, and aryl, or R.sub.13 is a spacer group connecting at
least two compounds of the above formula to form a di- or
multi-functional maleimide; and MI is ##STR27##
wherein R.sub.10 and R.sub.11 are as defined above.
25. The method of claim 24, wherein said aromatic maleimide is
selected from the group consisting of phenyl maleimide,
N-(2-CF.sub.3 -phenyl)maleimide, N-(2-t-butylphenyl)maleimide,
N-(2-CF.sub.3 -phenyl)methylmaleimide,
N-(2,4,6-isopropyl-3-maloimide phenyl)maleimide,
N-(2-iodophenyl)maleimide, N-(2-bromo-3,5-CF.sub.3
-phenyl)maleimide, di(4-maleimido phenyl)methane,
N-(2-chlorophenyl) maleimide, N-(2-bromophenyl) maleimide,
N-(2-fluorophenyl) maleimide, N-(4-CF.sub.3 -phenyl) maleimide,
di(3,5-diethyl-4-maleimidophenyl)methane, and mixtures thereof.
26. A method of polymerizing a compound having at least one
ethylenically unsaturated double bond, comprising exposing said
compound to radiation in the presence of at least one maleimide
compound of the formula ##STR28##
wherein each R.sub.1 and R.sub.2 is independently selected from the
group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl, aryl,
alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a fused
substituted or unsubstituted saturated or unsaturated five or six
membered cyclic hydrocarbon or heterocyclic ring system, and at
least one photoactive compound without a maleimide functionality,
wherein said maleimide compound initiates photopolymerization of
said ethylenically unsaturated compound and wherein said
photoactive compound sensitizes initiation of the ethylenically
unsaturated compound by said maleimide.
27. A method of polymerizing a compound having at least one
ethylenicaUy unsaturated double bond, comprising exposing said
compound to radiation in the presence of at least one maleic
anhydride of the formula ##STR29##
wherein each R.sub.1 and R.sub.2 is independently selected from the
group consisting of hydrogen, C1 to C10 alky), cycloalkyl, aryl,
alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a fused
substituted or unsubstituted saturated or unsaturated five or six
membered cyclic hydrocarbon or heterocyclic ring system, and at
least one photoactive compound without a maleimide functionality,
wherein said maleimide compound initiates photopolymerization of
said ethylenically unsaturated compound and wherein said
photoactive compound sensitizes initiation of the ethylenically
unsaturated compound by said maleic anhydride.
28. The method of claim 18, wherein said benzophenone compound has
the formula ##STR30##
wherein: B is (H,H), --CH.sub.2 --, --S--, --O--, --CO--,
--NR.sub.15 --, or a bond bridging the two aromatic rings; each
R.sub.14 is independently selected from the group consisting of
hydrogen, alkyl, cycloalkyl, alkoxy, aryl, alkylaryl, arylalkyl,
halogen, trihaloalkyl, --CN, --NO.sub.2, --C(O)OR.sub.15,
--C(O)R.sub.15, --OR.sub.15, --N(R.sub.15).sub.2,
--OC(O)CR.sub.15.dbd.CHR.sub.15, R.sub.16, --OR.sub.16, --R.sub.17
--OC(O)CR.sub.15.dbd.CHR.sub.15, polymerizable moieties, and
oligomeric and polymeric moieties; R.sub.15 is selected from the
group consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl,
and alkylaryl; R.sub.16 is one or more saturated or unsaturated
five or six membered hydrocarbon or heterocyclic ring system,
optionally substituted with one or more alkyl, cycloalkyl, or
halogen; and R.sub.17 is selected from the group consisting of
alkyl, aryl, cycloalkyl, arylalkyl, and alkylaryl.
29. The method of claim 18, wherein said benzophenone compound is
selected from the group consisting benzophenone, thioxanthone,
isopropylthioxanthone, chlorothioxanthone,
4-morpholinobenzophenone, 4,4'-diphenoxybenzophenone, methyl
o-benzoylbenzoate, 1-methyl-2-(2-ethylhexyloxy)thioxanthone,
4,4'-di-(4-isopropylphenoxy)benzophenone, acrylic acid
4-benzoylphenyl ester, 4,4'-diphenylbenzophenone,
4-phenylbenzophenone, and mixtures thereof.
30. The method of claim 18, wherein said at least one
photopolymerizable compound is selected from the group consisting
of monomers and oligomers derived from acrylic and methacrylic
acid, optionally dispersed or dissolved in a solvent that is
copolymerizable therewith.
31. The method of claim 30, wherein said photopolymerizable
compound is selected from the group consisting of methyl acrylate,
ethyl acrylate, n- or tert-butylacrylate, isooctyl acrylate, methyl
methacrylate, ethylmethacrylate, 2-ethylhexyl methacrylate,
butylacrylate, isobutyl methacrylate, hydroxy acrylates, glycol
acrylates, allyl acrylates, epoxy acrylates, aminoplast acrylates,
acrylated epoxides, acrylated polyesters, acrylated polyurethanes,
and mixtures thereof.
32. The method of claim 18, wherein said composition further
comprises a hydrogen atom donor compound.
33. The method of claim 32, wherein said hydrogen atom donor
comprises a tertiary amine.
34. The method of claim 18, wherein said photopolymerizable
compound comprises a hydrogen atom donor molecular component.
35. The composition of claim 1, wherein said maleimide compound
comprises an aromatic maleimide of the formula ##STR31##
wherein: each R.sub.5, R.sub.6, R.sub.8, R.sub.9, R.sub.10 and
R.sub.11 is H; and R.sub.7 is a spacer group connecting at least
two compounds of the above formula to form a di- or
multi-functional maleimide.
36. The composition of claim 35, wherein said aromatic maleimide is
##STR32##
37. The composition of claim 1, wherein said photoactive
benzophenone compound comprises a benzophenone compound of the
formula ##STR33##
wherein: B is (H,H); at least one R.sub.14 is aryl and the other
R.sub.14 are hydrogen; R.sub.15 is selected from the group
consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl, and
alkylaryl; R.sub.16 is one or more saturated or unsaturated five or
six membered hydrocarbon or heterocyclic ring system, optionally
substituted with one or more alkyl, cycloalkyl, or halogen; and
R.sub.17 is selected from the group consisting of alkyl, aryl,
cycloalkyl, arylalkyl, and alkylaryl.
38. The composition of claim 37, wherein said benzophenone compound
is 4-phenylbenzophenone.
39. A photopolymerizable composition comprising at least one
photopolymerizable compound having at least one ethylenically
unsaturated double bond, di(4-maleimidophenyl)methane and
4-phenylbenzophenone.
40. A method of polymerizing a polymerizable compound having at
least one ethylenically unsaturated double bond, comprising
exposing said compound to radiation in the presence of
di(4-maleimidophenyl)methane and 4-phenylbenzophenone.
41. A photopolymerizable composition comprising at least one
photopolymerizable compound having at least one ethylenically
unsaturated double bond, at least one maleimide capable of
initiating photopolymerization of said ethylenically unsaturated
compound in an amount of about 0.01 to about 2 mole percent, and at
least one photoactive compound without a maleimide functionality
which is a sensitizer capable of sensitizing initiation of the
ethylenically unsaturated compound by said maleimide, wherein said
maleimide compound comprises an alkyl maleimide of the formula
##STR34##
wherein: each R.sub.1 and R.sub.2 is independently selected from
the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused substituted or unsubstituted saturated or unsaturated five or
six membered cyclic hydrocarbon or heterocyclic ring system; and R
is straight chain, branched or cyclic C1-C10 alkyl, optionally
substituted with one or more C1-C4 alkyl.
42. The composition of claim 41, wherein said alkyl maleimide is
selected form the group consisting of methyl maleimide, hexyl
maleimide, cyclohexyl maleimide, and mixtures thereof.
43. A photopolymerizable composition comprising at least one
photopolymerizable compound having at least one ethylenically
unsaturated double bond, at least one maleimide capable of
initiating photopolymerization of said ethylenically unsaturated
compound in an amount of about 0.01 to about 2 mole percent, and at
least one photoactive benzophenone compound which is a sensitizer
capable of sensitizing initiation of the ethylenically unsaturated
compound by said maleimide, wherein said benzophenone compound
comprises a compound of the formula ##STR35##
wherein: B is (H,H), --CH.sub.2 --, --S--, --CO--, --NR.sub.15 --,
or a bond bridging the two aromatic rings; each R.sub.14 is
independently selected from the group consisting of hydrogen,
alkyl, cycloalkyl, alkoxy, aryl, alkylaryl, arylalkyl, halogen,
trihaloalkyl, --CN, --NO.sub.2, --C(O)OR.sub.15, --C(O)R.sub.15,
--OR.sub.15, --N(R.sub.15).sub.2, --OC(O)CR.sub.15.dbd.CHR.sub.15,
R.sub.16, --OR.sub.16, --R.sub.17 --OC(O)CR.sub.15, polymerizable
moieties, and oligomeric and polymeric moieties; R.sub.15 is
selected from the group consisting of hydrogen, alkyl, aryl,
cycloalkyl, arylalkyl, and alkylaryl; R.sub.16 is one or more
saturated or unsaturated five or six membered hydrocarbon or
heterocyclic ring system, optionally substituted with one or more
alkyl, cycloalkyl, or halogen; and R.sub.17 is selected from the
group consisting of alkyl, aryl, cycloalkyl, arylalkyl, and
alkylaryl.
44. A photopolymerizable composition, comprising at least one
photopolymerizable compound having at least one ethylenically
unsaturated double bond, at least one maleimide capable of
initiating photopolymerization of said ethylenically unsaturated
compound in an amount of about 0.01 to about 2 mole percent, and at
least one photoactive benzophenone compound which is a sensitizer
capable of sensitizing initiation of the ethylenically unsaturated
compound by said maleimide, wherein said benzophenone compound is
selected from the group consisting benzophenone, thioxanthone,
isopropylthioxanthone, chloroxanthone, 4-morpholinobenzophenone,
4,4'-diphenoxybenzophenone, methyl o-benzoylbenzoate,
1-methyl-2-(2-ethylhexyloxy)thioxanthone,
4,4'-di-(4-isopropylphenoxy)benzophenone, acrylic acid
4-benzoylphenyl ester, 4,4'-diphenylbenzophenone,
4-phenylbenzophenone, and mixtures thereof.
45. A method of polymerizing a polymerizable compound having at
least one ethylenically unsaturated double bond, comprising
exposing said compound to radiation in the presence of at least one
maleimide compound in an amount of about 0.01 to about 2 mole
percent and at least one photoactive compound without a maleimide
functionality, wherein said maleimide initiates photopolymerization
of said ethylenically unsaturated compound and wherein said
photoactive compound sensitizes initiation of the ethylenically
unsaturated compound by said maleimide, wherein said maleimide
compound comprises an alkyl maleimide of the formula ##STR36##
wherein: each R.sub.1 and R.sub.2 is independently selected from
the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused substituted or unsubstituted saturated or unsaturated five or
six membered cyclic hydrocarbon or heterocyclic ring system; and R
is straight chain, branched or cyclic C1-C10 alkyl, optionally
substituted with one or more C1-C4 alkyl.
46. The method of claim 45, wherein said alkyl maleimide is
selected form the group consisting of methyl maleimide, hexyl
maleimide, cyclohexyl maleimide, and mixtures thereof.
47. A method of polymerizing a polymerizable compound having at
least one ethylenically unsaturated double bond, comprising
exposing said compound to radiation in the presence of at least one
maleimide compound in an amount of about 0.01 to about 2 mole
percent and at least one photoactive benzophenone compound without
a maleimide functionality, wherein said maleimide initiates
photopolymerization of said ethylenically unsaturated compound and
wherein said photoactive benzophenone compound sensitizes
initiation of the ethylenically unsaturated compound by said
maleimide, wherein said benzophenone compound has the formula
##STR37##
wherein: B is (H,H), --CH.sub.2 --, --S--, --O--, --CO--,
--NR.sub.15 --, or a bond bridging the two aromatic rings; each
R.sub.14 is independently selected from the group consisting of
hydrogen, alkyl, cycloalkyl, alkoxy, aryl, alkylaryl, arylalkyl,
halogen, trihaloalkyl, --CN, --NO.sub.2, --C(O)OR.sub.15,
--C(O)R.sub.15, --OR.sub.15, --N(R.sub.15).sub.2,
--OC(O)CR.sub.15.dbd.CHR.sub.15, R.sub.16, --OR.sub.16, --R.sub.17
--OC(O)CR.sub.15.dbd.CHR.sub.15, polymerizable moieties, and
oligomeric and polymeric moieties; R.sub.15 is selected from the
group consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl,
and alkylaryl; R.sub.16 is one or more saturated or unsaturated
five or six membered hydrocarbon or heterocyclic ring system,
optionally substituted with one or more alkyl, cycloalkyl, or
halogen; and R.sub.17 is selected from the group consisting of
alkyl, aryl, cycloalkyl, arylalkyl, and alkylaryl.
48. A method of polymerizing a polymerizable compound having at
least one ethylenically unsaturated double bond, comprising
exposing said compound to radiation in the presence of at least one
maleimide compound in an amount of about 0.01 to about 2 mole
percent and at least one photoactive benzophenone compound without
a maleimide functionality, wherein said maleimide initiates
photopolymerization of said ethylenically unsaturated compound and
wherein said photoactive benzophenone compound sensitizes
initiation of the ethylenically unsaturated compound by said
maleimide, wherein said benzophenone compound is selected from the
group consisting benzophenone, thioxanthone, isopropylthioxanthone,
chlorothioxanthone, 4-morpholinobenzophenone,
4,4'-diphenoxybenzophenone, methyl o-benzoylbenzoate,
1-methyl-2-(2-ethylhexyloxy)thioxanthone,
4,4'-di-(4-isopropylphenoxy)benzophenone, acrylic acid
4-benzoylphenyl ester, 4,4'-diphenylbenzophenone,
4-phenylbenzophenone, and mixtures thereof.
49. The method of claim 18, wherein said maleimide compound
comprises an aromatic maleimide of the formula ##STR38##
wherein: each R.sub.5, R.sub.6, R.sub.8, R.sub.9, R.sub.10 and
R.sub.11 is H; and R.sub.7 is a spacer group connecting at least
two compounds of the above formula to form a di- or
multi-functional maleimide.
50. The method of claim 49, wherein said aromatic maleimide is
##STR39##
51. The method of claim 18, wherein said photoactive compound
comprises a benzophenone compound of the formula ##STR40##
wherein: B is (H,H); at least one R.sub.14 is aryl and the other
R.sub.14 are hydrogen; R.sub.15 is selected from the group
consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl, and
alkylaryl; R.sub.16 is one or more saturated or unsaturated five or
six membered hydrocarbon or heterocyclic ring system, optionally
substituted with one or more alkyl, cycloalkyl, or halogen; and
R.sub.17 is selected from the group consisting of alky, aryl;
cycloalkyl, arylalkyl, and alkylaryl.
52. The method of claim 51, wherein said benzophenone compound is
4-phenylbenzophenone.
53. A method of polymerizing a polymerizable compound having at
least one ethylenically unsaturated double bond, comprising
exposing said compound to radiation in the presence of at least one
maleimide compound in an amount of about 0.01 to about 2 mole
percent and at least one photoactive benzophenone compound, wherein
said maleimide initiates photopolymerization of said ethylenically
unsaturated compound and wherein said photoactive benzophenone
compound sensitizes initiation of the ethylenically unsaturated
compound by said maleimide, wherein said photoactive benzophenone
compound comprises a benzophenone compound of the formula
##STR41##
wherein: B is (H,H); at least one R.sub.14 is aryl and the other
R.sub.14 are hydrogen; R.sub.15 is selected from the group
consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl, and
alkylaryl; R.sub.16 is one or more saturated or unsaturated five or
six membered hydrocarbon or heterocyclic ring system, optionally
substituted with one or more alkyl, cycloalkyl, or halogen; and
R.sub.17 is selected from the group consisting of alkyl, aryl,
cycloalkyl, arylalkyl, and alkylaryl.
54. The method of claim 53, wherein said benzophenone compound is
4-phenylbenzophenone.
55. The composition of claim 9, wherein said maleimide is present
in an amount of about 0.01 to about 2 mole percent.
56. The composition of claim 9, wherein said photoactive compound
is a benzophenone compound.
57. The composition of claim 10, wherein said maleimide is present
in an amount of about 0.01 to about 2 mole percent.
58. The composition of claim 10, wherein said photoactive compound
is a benzophenone compound.
59. The method of claim 26, wherein said maleimide is present in an
amount of about 0.01 to about 2 mole percent.
60. The method of claim 26 wherein said photoactive compound is a
benzophenone compound.
61. The method of claim 27, wherein said maleimide is present in an
amount of about 0.01 to about 2 mole percent.
62. The method of claim 27, wherein said photoactive compound is a
benzophenone compound.
63. The composition of claim 41, wherein said photoactive compound
is a benzophenone compound.
64. The method of claim 45, wherein said photoactive compound is a
benzophenone compound.
Description
FIELD OF THE INVENTION
This invention relates generally to photopolymerizable compositions
and more particularly to photopolymerizable compositions which
include maleimide compounds as a component and methods of using the
same.
BACKGROUND OF THE INVENTION
Ethylenically unsaturated compounds, such as acrylate derivatives,
can be polymerized by exposure to radiation, typically ultraviolet
light, in the presence of a photoinitiating system. Typically, the
photoinitiating system includes (1) a compound capable of
initiating polymerization of the ethylenically unsaturated compound
upon exposure to radiation (a "photoinitiator") and optionally (2)
a coinitiator or synergist, that is, a molecule which serves as a
hydrogen atom donor. The coinitiators or synergists are typically
alcohols, tertiary amines, amides, or ethers which have labile
hydrogens attached to a carbon adjacent to a heteroatom. Currently
commercially available photoinitiators include benzophenones and
derivatives thereof, such as thioxanthone derivatives.
Maleimides, and in particular N-aliphatic and ortho-substituted
(i.e. "twisted") N-aromatic maleimides have been investigated as
comonomer-photoinitiators of UV-curable acrylic systems. These
maleimides have been observed to require the presence of a hydrogen
atom-donor synergist (such as an amine, ether, thiol, or the like)
to obtain reasonable rates of initiation and polymerization.
J. Put and F. C. De Schryver, "Photochemistry of Nonconjugated
Bichromophoric Systems," Journal of the American Chemical Society.
95, 1, 137-45 (1973); "Photocyloaddition Polymerization. I.
Preparation and Characterization of
Poly-N,N'-polymethylenebisdichloromaleimides," Journal of Polymer
Science: Part A-1. 8, 1939-48 (1970); and N. Boens et al.,
"Solid-State Ultraviolet Irradiation of Some Maleimides and
Bismaleimides," Journal of Polymer Science: Polymer Chemistry
Edition 13, 210-13 (1975) report studies of the sensitization of
maleimides with benzophenone and thioxanthones for the formation of
maleimide 2+2 cycloadducts. F. C. De Schryver, et al,
"Photochemistry of Nonconjugated Bichromophoric Systems.
Photopolymerization of N,N-Alkylenebis (dimethylmaleimides),"
Journal of the American Chemical Society 96, 20, 6463-69 (1974)
also report the formation polymer networks by the sensitized
step-wise 2+2 cycloaddition of maleimides.
SUMMARY OF THE INVENTION
The present invention is directed to photopolymerizable
compositions and methods for radiation curing of the same. The
compositions of the invention include at least one radiation
curable compound. The compositions preferably include ethylenically
unsaturated compounds, and in particular, acrylate derivatives.
The compositions further include at least one maleimide which is
capable of initiating the photopolymerization of a radiation
curable compound. The maleimide can be an alkyl maleimide,
functionalized aliphatic maleimide, aromatic maleimide, maleimide,
maleic anhydride, or mixtures thereof. The maleimide component can
be substantially completely consumed during initiation and
photopolymerization (incorporated into the polymer structure).
The composition further includes additional photoactive compounds
as sensitizers. Specifically, the composition includes at least one
benzophenone compound which is capable of initiating polymerization
of the ethylenically unsaturated compound upon exposure to
radiation. As used herein, the term "benzophenone compound"
includes benzophenone and derivatives thereof, including
thioxanthone and derivatives of thioxanthone. In addition, the
composition optionally includes at least one coinitiator or
synergist as a hydrogen atom donor or an electron donor. The
hydrogen atom donor can be present as a separate compound or can be
included as a molecular component of the photopolymerizable
compound. The synergistic effect described herein which occurs when
a sensitizer is used in conjunction with a maleimide in the
presence of a hydrogen atom donor has been observed to dramatically
increase rates of polymerization of typical acrylic photo-curable
systems, as compared to rates obtained using the same acrylic
photo-curable system with either maleimide with a hydrogen-atom
donor or the sensitizer with a hydrogen-atom donor as the
initiating system.
The present invention also provides methods for radiation curing of
photopolymerizable compositions of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Some of the features and advantages of the invention having been
described, others will become apparent from the detailed
description which follows, and from the accompanying drawings, in
which:
FIG. 1 is a graph illustrating photo-differential scanning
calorimetry (DSC) exotherm rates for the photopolymerization of
1,6-hexanediol diacrylate (HDDA) with photoinitiator packages of 3%
benzophenone (BZPN)/1% methyl diethanol amine (NMDEA) and 0.31%
N-methyl maleimide (MMI)/1% NMDEA;
FIG. 2 is a graph illustrating photo-DSC exotherm rates for the
photopolymerization of polyethylene glycol diacrylate (PEG 400 DA)
with photoinitiator packages of 3% BZPN/1% NMDEA and 0.31% MMI/1%
NMDEA;
FIG. 3 is a graph illustrating photo-DSC exotherm rates for the
photopolymerization of HDDA with photoinitiator packages of 3%
BZPN/1% NMDEA, 0.31% MMI/1% NMDEA, and 3% BZPN/0.31% MMI/1%
NMDEA;
FIG. 4 is a graph illustrating photo-DSC exotherm rates for the
photopolymerization of HDDA with photoinitiator packages of 3%
BZPN/0.31% n-phenyl maleimide (N-PHMI)/1% NMDEA, 3% BZPN/0.31%
N-hexyl maleimide (N-HMI)/1% NMDEA, 3% BZPN/0.31% N-cyclohexyl
maleimide (N-CHMI)/1% NMDEA, 3% BZPN/0.31% maleic anhydride/1%
NMDEA, and 3% BZPN/3% Irgacure 651 (.alpha.,.alpha.-dimethoxy
deoxybenzoin (BDK)); and
FIG. 5 is a graph illustrating photo-DSC exotherm rates for the
photopolymerization of HDDA with photoinitiator packages of 3%
BZPN/0.31% maleimide (MI)/1% NMDEA, 3% BZPN/0.31%
N-2-n-tert-butyl-phenyl maleimide/1% NMDEA, 3% BZPN/0.31% DEFMR
(diethylfumarate)/1% NMDEA, 3% BZPN/0.31% HMI/1% NMDEA, and 3%
BZPN/0.31% maleic anhydride/1% NMDEA.
DETAILED DESCRIPTION OF THE INVENTION
Maleimides useful in the compositions of the invention include
maleimides of the formula ##STR1##
and maleic anhydrides of the formula ##STR2##
wherein: each R.sub.1 and R.sub.2 is independently selected from
the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused saturated or unsaturated five or six membered cyclic
hydrocarbon or heterocyclic ring system containing one or two O, N
or S atoms, optionally substituted with alkyl, aryl, halogen,
arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and
the like. Such compounds are commercially available and/or can be
prepared using commercially available starting materials using
techniques known in the art.
Alkyl maleimides useful in the invention include compounds having
at least one maleimide functional group substituted with a linear,
branched or cyclic C1-C10 alkyl radical at the nitrogen atom.
Exemplary alkyl maleimide compounds can have the formula below:
##STR3##
wherein: each R.sub.1 and R.sub.2 is independently selected from
the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused saturated or unsaturated five or six membered cyclic
hydrocarbon or heterocyclic ring system containing one or two O, N
or S atoms, optionally substituted with alkyl, aryl, halogen,
arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and
the like; and R is straight chain, branched or cyclic C1-C10 alkyl,
optionally substituted with one or more C1-C4 alkyl, and preferably
is C1-C4 alkyl or C6 cycloalkyl.
Exemplary alkyl maleimides include without limitation methyl
maleimide, hexyl maleimide, cyclohexyl maleimide, and the like.
Such compounds are known in the art and can be prepared using
techniques known in the art. See, for example, Z. Y. Wang,
Synthetic Comm. 20(11) 1607-1610 (1990); P. O. Tawney et al., J.
Org. Chem. 26, 15 (1961); and U.S. Pat. No. 2,542,145.
Aliphatic maleimide compounds useful in the invention include
compounds having at least one maleimide unit substituted with a
functionalized aliphatic substituent at the nitrogen atom. The
aliphatic substituent preferably is a linear or branched C1 to C10
alkyl, and more preferably methyl or ethyl. The alkyl is optionally
substituted with C1 to C4 alkyl, C1 to C4 alkoxy, halogen, and the
like as described below.
Aliphatic maleimides useful in the invention can be monofunctional
(have one maleimide functional group), or can be di- or
multi-functional (have two or more maleimide functional groups).
For example, two or more aliphatic maleimide units can be connected
or coupled via a spacer group(s), such as, but not limited to,
linear or branched C1 to C10 alkyl, C3 to C6 cycloalkyl optionally
substituted with C1 to C4 alkyl, C1 to C10 oxyalkyl, which can
include one or more oxygen atoms, such as that derived from
ethylene glycol, carbonate, aryl, alkylaryl, arylalkyl, and the
like. Still further, maleimide compounds useful in the invention
include maleimide units connected to polymeric or oligomeric
compounds (typically having a molecular weight of at least about
1000). For example, unsaturated polyester resins with varying
percent maleimide functionality incorporated therein as known in
the art can be used.
Exemplary aliphatic maleimide compounds can have the formula below:
##STR4##
wherein: (a) each R.sub.1 and R.sub.2 is independently selected
from the group consisting of hydrogen, C1 to C10 alkyl, cycloalkyl,
aryl, alkoxy, and halogen, or R.sub.1 and R.sub.2 together form a
fused saturated or unsaturated five or six membered cyclic
hydrocarbon or i heterocyclic ring system containing one or two O,
N or S atoms, optionally substituted with alkyl, aryl, halogen,
arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and
the like; (b) R.sub.4 is linear or branched C1 to C10 alkyl,
heteroatom, or silicon --SiH.sub.2 --; and (c1) when R.sub.4 is C1
to C10 alkyl, FG is a functional group selected from the group
consisting of --OR.sub.3, --SR.sub.3, --SiH.sub.2
R.sub.3,--OC(O)N(R.sub.3).sub.2, --OC(O)C(.dbd.CHR.sub.3)R.sub.3,
--OC(O)R.sub.3, --C(O)R.sub.3, --N(R.sub.3).sub.2, --C(O)OR.sub.3,
--NCO, --C(O)N(R.sub.3).sub.2, --OC(O)OR.sub.3, --CN, halogen,
--CH.sub.2 N-aryl-FG', --CH.sub.2 N-aryl-R.sub.3 --FG', sulfonic
acid, quaternary ammonium, and salts thereof, in which each R.sub.3
is selected from the group consisting of hydrogen, alkyl, aryl,
cycloalkyl, arylalkyl, and alkylaryl, and in which FG' is selected
from the group consisting of --OR.sub.3, --SR.sub.3, --SiH.sub.2
R.sub.3, --OC(O)N(R.sub.3).sub.2, --OC(O)C(.dbd.CHR.sub.3)R.sub.3,
--OC(O)R.sub.3, --C(O)R.sub.3, --N(R.sub.3).sub.2, --C(O)OR.sub.3,
--NCO, --C(O)N(R.sub.3).sub.2, --OC(O)OR.sub.3, --CN, halogen,
sulfonic acid, and quaternary ammonium, or (c2) when R.sub.4 is a
heteroatom or silicon --SiH.sub.2 --, FG is selected from the group
consisting of hydrogen, alkyl, aryl, cycloalkyl, alkylaryl,
arylalkyl, alkyl-FG", and aryl-FG", wherein FG" is the same as FG'
as defined in (c1) above, or (c3) FG is a functional group as
defined in (c1) in combination with a spacer group linking said
maleimide unit with at least one other maleimide unit to form a di-
or multifunctional maleimide compound. Exemplary spacer groups
include without limitation linear or branched C1 to C10 alkyl, C3
to C6 cycloalkyl, optionally substituted with lower C1 to C4 alkyl,
C1 to C10 oxyalkyl, which can include one or more oxygen atoms,
such as that derived from ethylene glycol, carbonate, and the like.
Aliphatic maleimides useful in the invention are described, for
example, in pending U.S. application Ser. No. 08/917,024, filed
Aug. 22, 1997, titled "Polymerization Processes Using Aliphatic
Maleimides," and its corresponding published international
application PCT Publication No. WO 98/07759, the entire disclosure
of each of which is hereby incorporated by reference.
Exemplary aliphatic maleimides useful in the invention include, but
are not limited to: ##STR5## ##STR6##
and the like.
Generally, aliphatic maleimides which include at least one
maleimide unit as described above can be prepared using techniques
known in the art. See, for example, Z. Y. Wang, Synthetic Comm.
20(11) 1607-1610 (1990); P. O. Tawney et al., J. Org. Chem. 26, 15
(1961); and U.S. Pat. No. 2,542,145.
Aromatic maleimides useful in invention include compounds according
to formula below: ##STR7##
wherein: each of R.sub.5, R.sub.6, R.sub.7, R.sub.8, and R.sub.9 is
independently selected from the group consisting of H, CX.sub.3,
COOR.sub.12, COR.sub.12, OR.sub.12, CN, SR.sub.12,
N(R.sub.12).sub.2, R.sub.13, X, and MI; R.sub.10 and R.sub.11 each
is independently selected from the group consisting of H, C1 to C10
alkyl, preferably C1-C4 alkyl, more preferably CH.sub.3,
cycloalkyl, aryl, alkoxy, and halogen, preferably chloride, or
R.sub.1 and R.sub.2 together form a fused saturated or unsaturated
five or six membered cyclic hydrocarbon or heterocyclic ring system
containing one or two O, N or S atoms, optionally substituted with
alkyl, aryl, halogen, arylalkyl, alkylaryl, cycloalkyl, alkoxy,
heteroatoms, silicon, and the like; X is halide, preferably F, Cl,
Br, or I; R.sub.12 is selected from the group consisting of H,
lower alkyl, cycloalkyl, and aryl; R.sub.13 is selected from the
group consisting of lower alkyl, cycloalkyl, and aryl, or R.sub.13
is a spacer group connecting at least two compounds of the above
formula to form a di- or multi-functional maleimide; and MI is
##STR8## wherein R.sub.10 and R.sub.11 are as defined above. For
example, two or more aromatic maleimide units can be connected or
coupled via a spacer group(s), such as, but not limited to, linear
or branched C1 to C10 alkyl, C3 to C6 cycloalkyl optionally
substituted with C1 to C4 alkyl, C1 to C10 oxyalkyl, which can
include one or more oxygen atoms, such as that derived from
ethylene glycol, carbonate, aryl, alkylaryl,arylalkyl, and the
like. The spacer group can be, for example: ##STR9## wherein Y and
Z are each independently selected from C2 to C10 alkylene, m is an
integer from 1 to 10, and n is an integer from 1 to 10;
Exemplary aromatic maleimides useful in the invention include, but
are not limited to: ##STR10## ##STR11##
and the like.
Generally, aromatic maleimides can be prepared using techniques
known in the art, with slight modifications as noted herein. The
compounds, for example, can be synthesized using a two step method,
which begins with the reaction of a suitably substituted aromatic
amine with maleic anhydride (or a substituted maleic anhydride,
such as citraconic anhydride) in a polar solvent, such as
diethylether, to produce the amic acid in near quantitative yields.
The amic acid is then recovered from the solvent and residual
solvent and water can be removed from the recovered product.
The second step is acid catalyzed ring closure to form the imide.
This reaction is performed by dissolving the amic acid in a
suitable solvent, such as an organic hydrocarbon solvent such as
toluene, optionally with a small amount of cosolvent, such as
dimethylsulfoxide (DMSO), adding a catalytic amount of concentrated
sulfuric acid, heating the mixture, preferably to reflux, and
removing water through the water/solvent azeotrope. Excess solvent
can then be removed, and the residual concentrated solution of the
imide in solvent precipitated. The imide is then collected and
dried to remove water and residual solvent(s). The second step can
also give near quantitative yields. Aromatic maleimides useful in
the invention are described, for example, in pending provisional
application Serial No. 60/047,729, filed May 27, 1997, titled
"Aromatic Maleimides," and its corresponding published
international application PCT Publication No. WO 98/54134, the
entire disclosure of each of which is hereby incorporated by
reference.
As used herein, the term alkyl refers to linear or branched C1 to
C10 alkyl, such as but not limited to methyl, ethyl, propyl, butyl,
isopropyl, and the like, optionally substituted with halogen, aryl,
arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and
the like. The term alkoxy refers to linear or branched C1 to C10
alkoxy. The term cycloalkyl refers to C3 to C6 cycloalkyl, such as
but not limited to cyclopentyl and cyclohexyl, also optionally
substituted with halogen, aryl, alkyl, arylalkyl, alkylaryl,
alkoxy, heteroatoms, silicon and the like. The term aryl refers to
C3 to C10 cyclic aromatic groups such as but not limited to phenyl,
naphthyl, and the like, optionally substituted with halogen, alkyl,
arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and
the like. The term heteroatom refers to oxygen, sulfur, and
nitrogen.
The photopolymerizable compositions include at least one maleimide
as defined above as a component thereof, for example, as a
photoinitiator, a comonomer, and the like. As used herein; and as
will be appreciated by the skilled artisan, the term
photopolymerizable composition refers to compositions which harden
or cure upon exposure to radiation.
Generally the compositions of the invention include ethylenically
unsaturated compounds, including monomers and oligomers derived
from acrylic and methacrylic acid, optionally dispersed or
dissolved in a suitable solvent that is copolymerizable therewith,
and mixtures thereof, which are photopolymerizable when exposed to
a source of radiation (ultraviolet or UV radiation, or radiation
outside the UV spectrum), particularly free radical polymerizable
systems. As will be appreciated by the skilled artisan, the
photopolymerizable compounds can be monofunctional, or can include
two or more polymerizable ethylenically unsaturated groupings per
molecule.
Exemplary photopolymerizable compounds or precursors include, but
are not limited to, reactive vinyl monomers, including acrylic
monomers, such as acrylic and methacrylic acids, and their amides,
esters, salts and corresponding nitriles. Suitable vinyl monomers
include, but are not limited to, methyl acrylate, ethyl acrylate,
n- or tert-butylacrylate, isooctyl acrylate, methyl methacrylate,
ethylmethacrylate, 2-ethylhexyl methacrylate, butylacrylate,
isobutyl methacrylate, the corresponding hydroxy acrylates, i.e.,
hydroxy ethylacrylate, hydroxy propylacrylate, hydroxy ethylhexyl
methacrylate, glycol acrylates, i.e., ethylene glycol
dimethacrylate, hexamethylene glycol dimethacrylate, the allyl
acrylates, i.e., allyl methacrylate, diallyl methacrylate, the
epoxy acrylates, i.e., glycidyl methacrylate, and the aminoplast
acrylates, i.e., melamine acrylate. Others such as vinyl acetate,
vinyl and vinylidene halides and amides, i.e., methacrylamide,
acrylamide, diacetone acrylamide, vinyl and vinylidene esters,
vinyl and vinylidene ethers, vinyl and vinylidene ketones,
butadiene, vinyl aromatics, i.e., styrene, alkyl styrenes,
halostyrenes, alkoxystyrenes, divinyl benzenes, vinyl toluene, and
the like are also included. Prepolymers include acrylated epoxides,
polyesters and polyurethanes, and are typically combined with a
suitable monomer for viscosity control.
The photopolymerizable compounds may be polymerized to form
homopolymers or copolymerized with various other monomers.
The photopolymerizable compound can be present in the compositions
of the invention in amounts from about 0 to about 99.8, preferably
about 80 to about 99.8, percent by weight, based on the total
weight of the composition.
The maleimides can be used singly or as mixtures thereof, and are
useful as photopolymerization initiators. In this aspect of the
invention, the maleimide compounds can be present in the
photopolymerizable composition in an amount sufficient to initiate
polymerization thereof upon exposure to radiation. The composition
can include about 0.01 to about 100, preferably about 0.01 to about
20, more preferably about 0.01 to about 10, percent by weight
maleimide compound, based on the total weight of the
photopolymerizable compounds. The inventors have found that only
relatively low concentrations of the maleimide are required for
desirable results. For example, the maleimide can be present in
amounts of about 0.01 mole percent to about 2 mole percent, and
even less than about 0.1 mole percent.
The benzophenone compound can be benzophenone or any derivative
thereof, including thioxanthone and derivatives thereof, and
mixtures of such compounds, having photoactive activity. Such
compounds are known in the art and include compounds of the
following structure: ##STR12##
wherein: B is (H,H), --CH.sub.2 --, --S--, --O--, --CO--,
--NR.sub.15 --, or a bond bridging the two aromatic rings; each
R.sub.14 is independently selected from the group consisting of
hydrogen, alkyl, cycloalkyl, alkoxy, aryl, alkylaryl, arylalkyl,
halogen, trihaloalkyl, --CN, --NO.sub.2, --C(O)OR.sub.15,
--C(O)R.sub.15, --OR.sub.15, --N(R.sub.15).sub.2,
--OC(O)CR.sub.15.dbd.CHR.sub.15, R.sub.16, --OR.sub.16, --R.sub.17
--OC(O)CR.sub.15.dbd.CHR.sub.15, polymerizable moieties, and
oligomeric and polymeric moieties; R.sub.15 is selected from the
group consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl,
and alkylaryl; R.sub.16 is one or more saturated or unsaturated
five or six membered hydrocarbon or heterocyclic ring system,
optionally substituted with one or more alkyl, cycloalkyl, or
halogen; and R.sub.17 is selected from the group consisting of
alkyl, aryl, cycloalkyl, arylalkyl, and alkylaryl.
The term polymerizable moiety refers to ethylenically unsaturated
moieties known in the art which are capable of reaction with
another compound (for example, by a free radical mechanism), such
as but not limited to, acrylate and methacrylate moieties. For
example, R.sub.14 can have the structure --(CH.sub.2).sub.n
--OC(O)--CRH.dbd.CH.sub.2 wherein n is an integer from 1 to 10 and
R is H or lower alkyl. Another exemplary polymerizable entity is a
maleimide moiety as described above.
The terms oligomeric and polymeric moieties refer to a moiety
including two or more monomer units (dimer, trimer, etc.),
typically having a molecular weight of at least about 500, and
higher. Thus the benzophenone compound can be an oligomer or
polymer having one or more benzophenone functionalities
incorporated therein (along the backbone and/or side chain).
Exemplary oligomeric and polymeric moieties include but are not
limited to a C2-C20 alkylene or polyalkylene polyol, wherein
hydroxy groups of the polyol moiety are optionally alkylated, and
preferably an alkylene or polyalkylene polyol derived from ethylene
glycol. Other suitable oligomer or polymer moieties include C2-C20
alkylene or polyalkylene moieties end capped with trihaloalkyl, and
optionally substituted with one or more halogen atoms along the
chain, preferably fluorine. Other exemplary oligomeric or polymer
moieties include C2-C20 alkylene or polyalkylene moieties including
carbonate groups and end capped with lower alkyl. Other exemplary
oligomeric or polymeric moieties include polyether ketones and
polyacrylate and polymethacrylate based compounds. Such oligomeric
and polymeric benzophenones are known in the art and are
commercially available.
Exemplary benzophenone compounds useful in the invention include
without limitation benzophenone, thioxanthone,
isopropylthioxanthone, chlorothioxanthone, methyl
o-benzoylbenzoate, 4-morpholinobenzophenone,
4,4'-diphenoxybenzophenone,
1-methyl-2-(2-ethylhexyloxy)thioxanthone,
4,4'-di-(4-isopropylphenoxy)benzophenone, acrylic acid
4-benzoylphenyl ester, 4,4'-diphenylbenzophenone,
4-phenylbenzophenone, and the like, as well as mixtures thereof.
These and other benzophenone compounds are in known in the art and
are commercially available or can be produced using commercially
available starting materials. The benzophenone photoinitiator can
be present in an amount ranging from about 0.001 to about 5 percent
by weight, based on the total weight of the composition.
The sensitizer package also includes at least one coinitiator or
synergist, that is, a molecule which serves as a hydrogen atom
donor or an electron donor. Coinitiators or synergists are known in
the art, and are typically alcohols, tertiary amines or ethers
which have available hydrogens attached to a carbon adjacent to a
heteroatom. The hydrogen atom donor can be present as a separate
compound or can be included as a molecular component of the
photopolymerizable compound (for example, polyethylene glycol
diacrylate). Such coinitiators when a separate component are
typically present in an amount between about 0.1 and about 5
percent by weight based on the total weight of the composition.
When present as a molecular component of a photopolymerizable
compound, the hydrogen atom donor component can be up to about 85
weight percent, and higher, of the photopolymerizable compound.
Suitable compounds include, but are not limited to,
triethanolamine, methyl-diethanolamine, ethyldiethanolamine and
esters of dimethylamino benzoic acid. Other known coinitiators or
accelerators can also be used.
The photopolymerizable compositions of the invention may also
contain other conventional agents, such as polymerization
inhibitors, fillers, ultraviolet absorbers, organic peroxides,
dyes, pigments, and the like.
The photopolymerizable compositions can be applied or deposited on
a surface of a substrate using conventional techniques and
apparatus. The composition can be applied as a substantially
continuous film. Alternatively, the composition can be applied in a
discontinuous pattern. The thickness of the deposited composition
can vary, depending upon the desired thickness of the resultant
cured product.
Typically, the substrate is coated with the uncured
photopolymerizable composition and passed under a commercially
available UV or excimer lamp on a conveyer moving at predetermined
speeds. The substrate to be coated can be, for example, metal,
wood, mineral, glass, paper, plastic, fabric, ceramic, and the
like.
The active energy beams used in accordance with the present
invention may be visible light or ultraviolet light or may contain
in their spectra both visible and ultraviolet light. The
polymerization may be activated by irradiating the composition with
ultraviolet light using any of the techniques known in the art for
providing ultraviolet radiation, i.e., in the range of 200 nm and
450 nm ultraviolet radiation, and especially with the 308 nm
emission from xenon chloride exciter lamps, commercially available
from Fusion Systems, or by irradiating the composition with
radiation outside of the ultraviolet spectrum. The radiation may be
natural or artificial, monochromatic or polychromatic, incoherent
or coherent and should be sufficiently intense to activate the
photoinitiators of the invention and thus the polymerization.
Conventional radiation sources include fluorescent lamps, excimer
lamps, mercury, metal additive and arc lamps. Coherent light
sources include pulsed nitrogen, xenon, argon ion- and ionized neon
lasers whose emissions fall within or overlap the ultraviolet or
visible absorption bands of the compounds of the invention.
The compositions are useful in any of the types of applications
known in the art for photopolymerizations, including as a binder
for solids to yield a cured product in the nature of a paint,
varnish, enamel, lacquer, stain or ink. The compositions can also
be useful in the production of photopolymerizable surface coatings
in printing processes, such as lithographic printing, screen
printing, and the like. The compositions can also be useful in
applications in which the compositions are applied to articles
which are to be exposed to the environment, such as signage.
Radiation cured coatings produced using conventional
photoinitiators typically degrade over time (as evidenced by
yellowing, increasing brittleness, and the like), which degradation
is exacerbated by direct exposure to sunlight. In contrast,
radiation cured coatings prepared using the maleimide compounds can
exhibit minimal degradation over time, even when exposed to direct
sunlight. The maleimides can also be water soluble.
The present invention will be further illustrated by the following
non-limiting examples.
EXAMPLE 1
Synthesis of Hydroxy Methylmaleimide (HMMI)
Maleimide (10 g, 0.103 mol) was added to 10 mL of a 37% solution of
formaldehyde and 0.31 mL of a 5% solution of NaOH was added. Within
10 minutes all of the maleimide had dissolved and an exothermic
reaction proceeded. The solution was stirred for 2 hours where
white crystals were observed. The solution was placed in a freezer
overnight and the resulting crystals filtered and washed with ice
cold ethanol and diethyl ether. The white crystals were purified
twice by sublimation. See P. O. Tawney, R. H. Snyder, R. P. Conger,
K. A. Leibbrand, C. H. Stiteler, and A. R. Williams J. Org. Chem.
26, 15 (1961).m.p. 104-106.degree. C. (9.77 g, 74.6%). .sup.1 H-NMR
(Acetone-d.sub.6, .delta., ppm): 4.96 (2H, --CH.sub.2 --, s), 5.33
(1H, --OH, s), 6.93 (2H, --CH.dbd.CH--, s). .sup.13 C-NMR
(Acetone-d.sub.6, .delta., ppm): 60.9 (1C, --CH.sub.2 --), 135.6
(2C, --CH.dbd.CH--), 173.1 (1C, --C.dbd.O).
EXAMPLE 2
Synthesis of Hydroxy Ethylmaleimide (HEMI)
Ethanolamine (80.96 g, 1.32 mol) was added to 500 mL of ethanol and
cooled to 0.degree. C. using an ice bath.
3,6-Endoxo-1,2,3,6-tetrahydrophthalic anhydride (220.21 g, 1.32
mol) was added to the solution and allowed to stir overnight. The
yellow tinted crystals were used without purification. The solution
was refluxed for four hours with azeotropic removal of water. The
solution was cooled to 0.degree. C. and the resulting crystals
filtered (151.74 g, 54.95%). Removal of furan was facilitated by
refluxing the crystals in xylenes for 4 hours with quantitative
yield of hydroxy ethylmaleimide after purification by sublimation
to yield white crystals, --CH.sub.2 O--), 134.2 (2C,
--CH.dbd.CH--), 171.2 (2C, --NC.dbd.O m.p. 68.degree. C. .sup.1
H-NMR (CDCl.sub.3, .delta., ppm): 2.62 (1H, --OH, s), 3.82-3.77
(4H, --NCH.sub.2 CH.sub.2 O--, overlapping), 6.76 (2H,
--CH.dbd.CH--, s). .sup.13 C-NMR (CDCl.sub.3, .delta., ppm): 40.5
(1C, --NCH.sub.2 --), 60.5 (1C,).
EXAMPLE 3
Triethylene Glycol Biscarbonate Bisethylmaleimide (TEGBCBEMI)
HEMI (25.65 g, 0.182 moles) and pyridine (14.38 g, 0.182 moles)
were dissolved in THF (130 mL) and the solution was stirred at room
temperature. Triethylene glycol bischloroformate (25.0 g, 0.091
moles) was added dropwise and stirred for 90 minutes. The pyridine
salt was filtered off and the solution was combined with 200 mL of
a 1N HCl solution. The product was extracted with methylene
chloride and washed with a 1N HCl solution followed by water and
then dried over magnesium sulfate. The red solution was diluted to
a volume of 150 mL and purified by column chromatography (2.5
cm.times.21 cm) using silica gel as the packing and methylene
chloride as the mobile phase yielding white crystals, m.p.
65.degree. C. (26.75 g, 60.76%). .sup.1 H-NMR (CDCl.sub.3),
.delta., ppm): 3.64-3.68 (4H .phi.-OCH.sub.2 --, t), 3.69-3.74 (4H,
.epsilon.-OCH.sub.2 --, t), 3.81-3.86 (4H, --NCH.sub.2 --, t),
4.26-4.3 (8H, --CH.sub.2 O(C.dbd.O)OCH.sub.2 --, t), 6.75 (4H,
--CH.dbd.CH--, s). .sup.13 C-NMR (CDCl.sub.3, .delta., ppm): 36.6
(2C, --NCH.sub.2 --), 64.7 (2C), 67.3 (2C), 68.8 (2C), 70.6 (2C),
134.4 (4C, --CH.dbd.CH--), 154.8 (2C, O(C.dbd.O)O), 170.4 (4C,
--NC.dbd.O).
EXAMPLE 4
Synthesis of 2-Ethylcarbonate Ethylmaleimide (2ECEMI)
Hydroxy ethylmaleimide (29.87 g, 0.212 moles) and pyridine (16.7 g,
0.212 moles) were dissolved in THF (170 mL) and the solution was
stirred at room temperature. Ethyl chloroformate (22.97 g, 0.212
moles) was added dropwise and stirred for 90 minutes. The pyridine
salt was filtered off and the solution was combined with 200 mL of
a 1N HCl solution. The product was extracted with methylene
chloride and washed with a 1N HCl solution followed by water and
then dried over magnesium sulfate. The red solution was
concentrated and the red crystals purified by sublimation yielding
white crystals, m.p. 52.degree. C. (34.76 g, 77.04%). .sup.1 H-NMR
(CDCl.sub.3), .delta., ppm): 1.26-1.34 (3H, --CH.sub.3, t),
3.81-3.87 (2H--NCH.sub.2 --, t), 4.14-4.25 (2H, .delta.-CH.sub.2
OC.dbd.O, q), 4.25-4.30 (2H, .beta.-CH.sub.2 O--, t), 6.74 (2H,
--CH.dbd.CH--, s). .sup.13 C-NMR (CDCl.sub.3, .delta., ppm): 14.2
(1C, --CH.sub.3), 36.8 (1C, --NCH.sub.2 --), 64.3 (1C,
.delta.-CH.sub.2 O), 64.5 (1C, .beta.-CH.sub.2 --), 134.4 (2C,
--CH.dbd.CH--), 154.9 (1C, O(C.dbd.O)O), 170.4 (2C, --C.dbd.O).
EXAMPLE 5
Synthesis of 2-Isopropyl Urethane Ethylmaleimide (2IPUEM)
Hydroxy ethylmaleimide (5 g, 35.4 mmol) was dissolved in 75 mL of
methylene chloride 1 drop of dibutyl tin dilaurate catalyst was
added. Isopropyl isocyanate (3.01 g, 35.4 mmol) was added dropwise
and the solution was stirred for 3 hours. The solution was washed
with water dried with magnesium sulfate. Concentration yielded
white crystals which were further purified sublimation yielding
white crystals, m.p. 117.degree. C. (6.49 g, 81%). .sup.1 H-NMR
(CDCl.sub.3, .delta., ppm): 1.11-1.14 (6H, --C(CH.sub.3).sub.2, d),
3.74-3.79 (2H, --NCH.sub.2 --, t), 4.28-4.32 (2H, --CH.sub.2 --,
t), 4.44-4.53 (1H, --CH--, p), 6.72 (2H, --OC--CH.dbd.CH--CO--, s).
NMR .sup.13 C-NMR (CDCl.sub.3, .delta., ppm): 170.5 (2C, C.dbd.O,
maleimide), 155.1 (1C, C.dbd.O, urethane), 134.2 (2C,
--CH.dbd.CH--), 61.7 (1C, .beta.-CH.sub.2), 43.6 (1C, --CH--), 37.4
(1C, .alpha.-CH.sub.2), 22.9 (2C, --CH.sub.3).
EXAMPLE 6
Synthesis of 2-Acryloyl Ethylmaleimide (2AEMI)
2-Hydroxyethyl maleimide (5 g, 35.4 mmol) and Et.sub.3 N (4.25 g,
43.0 mmol) was dissolved in 75 mL of methylene chloride and cooled
to 0.degree. C. Acryloyl chloride (3.20 g, 35.4 mmol) in 25 mL of
methylene chloride was added dropwise over 30 minutes. The solution
was stirred at room temperature for 30 minutes followed by
refluxing for 1 hour. The triethylamine hydrochloride was removed
by filtration and the yellow solution was concentrated. The yellow
crystals were purified by sublimation yielding white crystals, m.p.
77-78.degree. C. (5.00 g, 72.3%). .sup.1 H-NMR (CDCl.sub.3,
.delta., ppm): 3.81-3.87 (2H, --NCH.sub.2 --, t) 4.22-4.33 (2H,
--OCH.sub.2 --, t), 5.81-5.85 (2H, CH.sub.2.dbd.CH, cis), 6.00-6.13
(1H, CH.sub.2.dbd.CH--, q), 6.34-6.42 (1H CH.sub.2.dbd.CH, trans),
6.73 (2H, --OC--CH.dbd.CH--CO--, s). .sup.13 C-NMR (CDCl.sub.3,
.delta., ppm): 170.4 (2C, C.dbd.O, maleimide), 165.8 (1C, C.dbd.O,
ester), 134.2 (2C, --CH.dbd.CH--), 131.45 (1C, --CH.dbd.), 127.9
(1C, CH.sub.2.dbd.), 61.5 (1C, .beta.-CH.sub.2 --), 36.8 (1C,
.alpha.-CH.sub.2 --).
EXAMPLE 7
Synthesis of Acetoxy Ethyl Maleimide (AcOEMI)
Maleic anhydride (172.32 g, 1.75 mol) was added to ethanolamine
(107.34 g, 1.75 mol) and dissolved in 500 mL of acetone while
stirring overnight in an ice bath. To the solution, 400 mL of
acetic anhydride (4.23 mol) was added with sodium acetate (144 g,
1.75 mol). The solution was heated to 80.degree. C. and stirred for
1 hour. The contents were poured into ice water and the acetic acid
neutralized with K.sub.2 CO.sub.3. The product was extracted with
methylene chloride and then dried using magnesium sulfate. The
product was purified by sublimation yielding white crystals, m.p.
76.degree. C. (44.1 g, 13.45%). .sup.1 H-NMR (CDCl.sub.3, .delta.,
ppm): 2.02 (3H, --CH.sub.3, s), 3.82-3.77 (2H, --NCH.sub.2 --, t),
4.25-4.20 (2H, --CH.sub.2 O--, t), 6.75 (2H, --CH.dbd.CH--, s).
.sup.13 C-NMR (CDCl.sub.3, .delta., ppm): 20.7 (1C, --CH3), 37.0
(1C, --NCH.sub.2 --), 61.5 (1C, --CH.sub.2 O--), 134.3 (2C,
--CH.dbd.CH--), 170.5 (2C, --NC.dbd.O), 170.8 (1C, --OC.dbd.O).
EXAMPLE 8
Synthesis of 4,9-Dioxa-1,12 Dodecane Bismaleimide
(4,9-DO-1,12-DDBMI)
4,9-Dioxa-1,12-dodecane diamine (25 g, 0.122 mol) was dissolved in
acetone and added dropwise to a solution of maleic anhydride (24 g
0.244 mol) in 120 mL of acetone under cooling using an ice bath in
a nitrogen atmosphere. The solution was stirred overnight and the
contents were then poured into water and the bismaleamic acid
filtered and washed with ethanol and diethylether.
The bismaleamic acid (29.96 g, 74.8 mmol) was dissolved in an
acetone 120 mL and triethylamine (41.7 mL, 0.300 mol) solution. The
solution was heated to reflux, where acetic anhydride (21.2 mL,
0.224 mol) was added dropwise, the solution was refluxed for 12
hours. The solution was added to ice water and the precipitate
filtered and dried. The sample was purified by column
chromatography using silica gel as the adsorbent and methylene
chloride as the mobile phase yielding white crystals, m.p.
65.degree. C. (5.5 g, 20.2%). .sup.1 H-NMR (CDCl.sub.3, .delta.,
ppm): 1.60-1.54 (2H, .epsilon.-CH.sub.2 --), 1.91-1.78 (2H,
.beta.-CH.sub.2 --), 3.44-3.28 (4H, --CH.sub.2 OCH.sub.2 --),
3.66-3.59 (2H, --NCH.sub.2 --, t), 6.70 (2H, --CH.dbd.CH--, s).
.sup.13 C-NMR (CDCl.sub.3, .delta., ppm): 26.4 (2C,
.epsilon.-CH.sub.2 --), 28.6 (2C, .beta.-CH.sub.2 --), 35.6 (2C,
--NCH.sub.2 --), 68.2, 70.7 (4C, --CH.sub.2 OCH.sub.2 --), 134.2
(2C, --CH.dbd.CH--), 170.8 (2C, --NC.dbd.O).
EXAMPLE 9
Synthesis of Isophorone bisurethane bisethylmaleimide
(IPBUBEMI)
Hydroxy ethylmaleimide (10 g, 0.141 mol) was dissolved in acetone
and purged with nitrogen while stirring in an ice bath. One drop of
dibutyl tin dilaurate was added to the solution. The isophorone
diisocyanate (30.5 g, 0.141 mol) was added dropwise over 2-3 hours.
The solution was allowed to stir overnight and a white precipitate
was obtained after solvent removal m.p. 105-112.degree. C. (40.5 g,
100%). .sup.1 H-NMR (D.sub.6 -DMSO, .delta., ppm): 3.63-3.58 (2H,
--NCH.sub.2 --), 4.08-4.03 (2H, --CH.sub.2 O--, t), 7.03 (2H,
--CH.dbd.CH--, s). .sup.13 C-NMR (D.sub.6 -DMSO, .delta., ppm):
134.5 (2C, --CH.dbd.CH--), 154.9 (2C, NHC.dbd.O), (170.7 (2C,
--NC.dbd.O).
EXAMPLE 10
Synthesis of Bispropyl Maleimide (PBMI)
Diaminopropane was dissolved in 100 mL of dimethyl acetamide (DMAC)
and added dropwise to a solution of maleic anhydride in DMAC under
cooling using an ice bath in a nitrogen atmosphere. The solution
was stirred overnight and the contents were then poured into water
and the bismaleamic acid filtered and washed with ethanol and
diethylether.
The bismaleamic acid (84.54 g, 0.312 mol) was dissolved in 312 mL
of an acetone and triethylamine (87 mL, 0.624 mol) solution. The
solution was heated to reflux and acetic anhydride (88 mL, 0.61
mol) was added dropwise through a reflux condenser and the solution
was refluxed for 12 hours. The solution was added to ice water and
the precipitate filtered and dried. The sample was purified by
column chromatography using silica gel as the adsorbent and
methylene chloride as the mobile phase yielding white crystals,
m.p. 166.degree. C. (19.28 g, 26.3%). .sup.1 H-NMR (CDCl.sub.3,
.delta., ppm): 2.00-1.86 (2H, --CH.sub.2 --, p), 3.57-3.50 (4H,
--NCH.sub.2 --, t), 6.71 (2H, --CH.dbd.CH--, s). .sup.13 C-NMR
(CDCl.sub.3, .delta., ppm): 27.3 (1C, --CH.sub.2 --), 35.3 (2C,
--NCH.sub.2 --), 134.2 (2C, --CH.dbd.CH--), 170.6 (2C,
--NC.dbd.O).
EXAMPLE 11
Synthesis of Bisethylmaleimide Carbonate (BEMIC)
Hydroxy ethylmaleimide (10.0 g, 70.1 mmol) was dissolved in a
solution of methylene chloride (71 mL) and triethylamine (9.87 mL,
70.8 mmol) and cooled with an ice bath to 0.degree. C. Triphosgene
(3.504 g, 12 mmol) was added over a period of 4 hours and the
resulting solution filtered. The supernatant was washed with 1N
hydrochloric acid, 5% potassium carbonate solution and water. The
solution was dried over magnesium sulfate and purified using
activated carbon to yield white crystals (4.0 g, 18.5%). .sup.1
H-NMR (CDCl.sub.3, .delta., ppm): 3.82 (4H, --NCH.sub.2 --, t),
4.27 (2H, --CH.sub.2 O--, t), 6.73 (2H, --CH.dbd.CH--, s). .sup.13
C-NMR (CDCl.sub.3, .delta., ppm): 36.6 (2C, --NCH.sub.2 --), 64.9
(2C, --CH.sub.2 O--), 134.2 (2C, --CH.dbd.CH--), 154.5 (1C,
C.dbd.O) 170.8 (2C, --NC.dbd.O).
EXAMPLE 12
Synthesis of N-(2-CF.sub.3 -phenyl)maleimide
32.5 g of maleic anhydride is placed in 700 mL diethylether and
allowed to dissolve. 41.48 mL of 2-trifluoromethyl aniline is added
squirtwise to the stirring solution. The reaction is allowed to
proceed at room temperature overnight and a pale white precipitate
is observed. The stirring solution is then warmed for several hours
and filtered, yielding a pale white solid. The mother liquor is
then combined with the wash liquor and allowed to stir again, and
additional product is filtered off. The solids are then combined
and dried in vacuum. Typical yields are 90-98%.
44.8 g of the maleamic acid is then placed in a three necked flask
with 100 mL toluene and 25 mL DMSO, and allowed to dissolve. 1.8 mL
of concentrated sulfuric acid is then added to the stirring
mixture, which is then heated to about 130.degree. C. The reaction
mixture is allowed to reflux for 4 hours or until an azeotrope is
no longer observed. Excess toluene is then removed via vacuum
distillation. The mixture is then added to stirring distilled water
to precipitate the imide and remove excess DMSO. The aqueous
suspension is allowed to stir overnight and is then filtered. The
pale white solid is then dried under vacuum to remove water, DMSO
and toluene. Yields are typically 90-97%.
Products from both steps are analyzed using .sup.1 H and .sup.13 C
NMR in d.sub.6 -DMSO. The maleamic acid is characterized by a broad
peak due to the acid proton near 13-14 ppm, a peak due to the amide
proton near 10 ppm, and two doublets due to the ene protons near
6.4 ppm in the proton spectra. The maleamic acid is also
characterized by two peaks near 165 ppm due to the two carbonyls in
the carbon spectrum. The maleimide is characterized by the absence
of the acid and amide proton peaks, and the single ene proton peak
shifted to near 7.6 ppm in the proton spectrum. In the carbon
spectrum the maleimide shows a single carbonyl peak near 170
ppm.
The melting point of N-(2-CF.sub.3 -phenyl)maleimide is measured
using DSC at a heating rate of 20.degree. C./min and found to be
115.91 C. (endotherm peak maximum). Heat of fusion is also
calculated to be 71.62 J/g.
EXAMPLE 13
Synthesis of N-(2-t-butylphenyl)maleimide
N-(2-t-butylphenyl)maleimide is also prepared as described in
Example 12, except substituting 2-trifluoromethyl aniline with
2-tert-butyl aniline. The melting point of
N-(2-t-butylphenyl)maleimide is measured using DSC at a heating
rate of 20.degree. C./min and is found to be 99.64 C. (endotherm
peak maxima). Heat of fusion is also calculated to be 94.02
J/g.
EXAMPLE 14
Synthesis of N-(2-CF.sub.3 -phenyl)methylmaleimide
N-(2-CF.sub.3 -phenyl)methylmaleimide is also prepared as described
in Example 12, except substituting citraconic anhydride for maleic
anhydride.
EXAMPLE 15
Synthesis of N-(2-iodo-phenyl)maleimide
N-(2-iodo-phenyl)maleimide is prepared as described in Example 12,
except substituting 2-trifluoromethyl aniline with
2-iodoaniline.
EXAMPLE 16
Synthesis of N-(2-bromo-3,5-CF.sub.3 -phenyl)maleimide
N-(2-bromo-3,5-CF.sub.3 -phenyl)maleimide is prepared as described
in Example 12, except substituting 2-trifluoromethyl aniline with
2-bromo-3,5-trifluoromethyl aniline.
EXAMPLE 17
Photopolymerization Using Benzophenone/Amine/Maleimide
Formulation
FIG. 1 is a graph illustrating photo-DSC exotherm rate results for
the photopolymerization of a typical UV curable monomer (HDDA is
1,6-hexanediol diacrylate) with photoinitiator packages of
benzophenone (BZPN)/1% methyl diethanol amine (NMDEA) and N-methyl
maleimide (MMI)/1% NMDEA. For the results in FIG. 1, the
concentrations were adjusted to give comparable initiator
absorbances. The benzophenone/NMDEA system generates a higher
exotherm peak rate and a shorter time is required to attain the
peak maximum as compared to the MMI/NMDEA system.
Similar results are illustrated in FIG. 2 for the
photopolymerization of polyethylene glycol (400) diacrylate (PEG
400 DA) which has abstractable hydrogens between the acrylate
functionalities. While it is possible to achieve somewhat faster
rates by using maleimides with groups that have abstractable
hydrogens (such as heteroatom containing groups), the rates
achieved are still quite small compared to conventional
photoinitiator systems.
FIG. 3 gives photo-DSC exotherm results in nitrogen saturated
systems that incorporate three components (benzophenone sensitizer,
methyl maleimide, and NMDEA) as the photoinitiator package for the
polymerization of HDDA. The exotherm rate maximum increased
dramatically when both methyl maleimide and benzophenone are
present as compared to the exotherm rates for systems in which
methyl maleimide/NMDEA are present or in which benzophenone/NMDEA
are used and maleimide has been excluded. In other words, the
synergistic effect on polymerization rate of having the N-alkyl
maleimide present is dramatic, resulting in a substantially faster
overall curing process under the conditions employed. The results
in FIG. 3 were attained for systems in which the samples were
exposed to the unfiltered 30 mW output of a medium pressure mercury
lamp similar in spectral output (but lower in overall intensity) to
the lamps used in the UV curing industry.
To extend the results shown in FIG. 3, exotherms were recorded for
the photopolymerization of HDDA initiated by exposing
benzophenone/N-alkyl maleimide/NMDEA and benzophenone/N-aryl
maleimide/NMDEA systems to the output of a filtered (365-nm mercury
line filter) source (FIGS. 4 and 5). When either an N-alkyl or an
N-aryl maleimide was used in combination with the benzophenone
sensitizer, a dramatic increase in the polymerization rate was
observed as compared to results using the benzophenone/NMDEA system
alone. Results for maleic anhydride (FIGS. 4 and 5) and
Irgacure-651 (BDK) (FIG. 4) are shown for comparison. FIGS. 4 and 5
indicate that N-alkyl maleimides of widely varying structures
(methyl maleimide MMI, hexyl maleimide HMI, and cyclohexyl
maleimide CHMI) as well as both ortho-substituted (i.e., twisted)
(tert-butyl maleimide NtBMI) N-aryl maleimides and simple
substituted or unsubstituted (i.e., planar) (phenyl maleimide
N-PMI) N-aryl maleimides (heretofore found to be ineffective upon
direct excitation), can be sensitized to have much greater
initiation efficiencies than benzophenone/NMDEA systems.
Although not wishing to be bound by any explanation of the
invention, it is currently believed that energy transfer occurs
from the exited state triplet of the benzophenone to the maleimide,
which then abstracts a hydrogen atom and initiates the
polymerization process.
EXAMPLE 18
Photopolymerization Using Thioxanthone/Amine/Maleimide
Formulations
Additional studies examined the use of benzophenone derivatives,
and in particular thioxanthone derivatives, to sensitize initiation
by maleimides. Three types of experiments were performed using
N-methyl maleimide and a variety of thioxanthone photoinitiators.
Specific thioxanthones (available from First Chemical Corporation)
include isopropyl thioxanthone (ITX), LTX having the formula
##STR13##
4-morpholinobenzophenone (XPI-115) having the formula ##STR14##
4,4'-diphenoxybenzophenone (XPI-113) having the formula
##STR15##
and XPI-133 having the formula ##STR16##
First, formulations with various photoinitiators were prepared
containing HDDA and NMDEA, with and without MMI. These formulations
were then tested by photo-differential scanning calorimetry
(photo-DSC), using a Xenon-doped mercury lamp at 25.degree. C.
using (1) a 313 nm band pass filter, (2) a 365 nm band pass filter,
and (3) the full arc of the lamp at different intensities.
313 nm Band Pass Filter (BPF) Experiments
At 313 nm, both the maleimide and the photoinitiator absorb
photons, with the relative absorbance depending of the ratio of the
respective molar extinction coefficients. Formulations were
prepared to have equal absorbance of different benzophenone
derivatives at 313 mrn. The experiments were performed in nitrogen,
with a filtered light intensity of about 1 mW/cm.sup.2.
The data in Table 1 show that when the maleimide is used in
conjunction with ITX and XPI-115 at these concentrations and under
these conditions, the average peak exotherm maximum (polymerization
rate) is enhanced. Also, enhanced relative conversions are obtained
when the maleimide is used in conjunction with ITX, XPI-113,
XPI-115, and XPI-133.
TABLE 1 Data from 313 nm BPF Photo-DSC Experiments Using HDDA
Average Average Formulation Exotherm Exotherm (mol % of Peak
Maximum Integration Photoinitiator compound) (W/g) (J/g) ITX 0.080%
ITX 28.32 554.35 0.86% MDEA 0.080% ITX 68.32 579.79 1.2% MDEA 0.66%
MMI LTX 0.0113% LTX 21.3 481.93 1.07% MDEA 0.0113% LTX 12.8 470.1
0.974% MDEA 0.608% MMI XPI-113 0.013% XPI-113 20.69 469.38 109%
MDEA 0.012% XPI-113 15.99 504.39 1.09% MDEA 0.56% MMI XPI-115
0.0025% XPI-115 24.42 481.9 1.18% MDEA 0.0025% XPI-115 29.59 489.51
1.07% MDEA 063% MMI XPI-133 0.0056% XPI-133 16.17 435.63 1.02% MDEA
0.0055% XPI-133 10.63 470.66 1.03% MDEA 0.607% MMI
365 nm BPF Experiments
A second set of photo-DSC experiments were performed which were
similar to those reported above except that a 365 nm band pass
filter was used in place of the 313 nm band pass filter. At 365 nm,
the principle absorbing species in these formulations should be the
photoinitiator. Exotherm data from these experiments are shown
below in Table 2.
TABLE 2 Data from 365 nm BPF Photo-DSC Experiments Using HDDA
Average Average Formulation Exotherm Exotherm (mol % Peak Maximum
Integration Photoinitiator of compound) (W/g) (J/g) ITX 0.090% ITX
18.13 447.69 0.942% MDEA 0.090% ITX 63.45 521.39 1.0% MDEA 0.62%
MMI LTX 0.013% LTX 23.77 508.91 1.07% MDEA 0.0113% LTX 42.96 509.14
0.974% MDEA 0.608% MMI
At these concentrations and under these conditions, there is
dramatic enhancement of the maximum rates of polymerization when
the maleimide is used in conjunction with ITX as well as with LTX.
There is also enhancement of the relative conversion when the
maleimide is included in the formulations. Absolute comparisons
between ITX and LTX should not be made using this data, as the
formulations were not prepared with equal photoinitiator absorption
at 365 nm.
Full Arc Experiments
Two formulations of HDDA with ITX, MDEA, with and without MMI were
also tested using the full arc of the lamp at three different
intensities, in nitrogen and in air. Peak exotherm maxima are
listed below in Table 3. In nitrogen, at low intensity (30
mW/cm.sup.2), the formulation with the maleimide is approximately
twice as efficient as that without. As the intensity increases to
100 and 300 mW/cm.sup.2, the ratio between with maleimide and
without decreases, while the absolute peak exotherm values continue
to increase, as expected. In air, at 30 mW/cm.sup.2, there is
little difference between the exotherms of the two formulations.
However, as the intensity increases to 100 and 300 mW/cm.sup.2, the
ratio (with MMI/without MMI) goes from 1.06 to 1.12 to 1.34, and
the exotherm peak values get larger.
TABLE 3 Data from full arc photo-DSC experiments with HDDA Exotherm
Peak Formulation Light Maximum (mol % of Intensity (W/g) compound)
(mW/cm.sup.2) Nitrogen Air 0.090% ITX 30 50 39 0.942% MDEA 100 73
64 300 97 77 0.090% ITX 30 -- 41 1.0% MDEA 0.61% 100 97 80 MMI 300
129 104
Short Duration Irradiation Photo-DSC Experiments
To investigate the performance of sensitized maleimide-acrylic
formulations in air a third battery of experiments was performed
using formulations of HDDA, MDEA, and ITX, and with and without
methyl maleimide. These photo-DSC experiments were performed at
25.degree. C. in nitrogen and in air with 1 second irradiation
times using a shuttered xenon-doped mercury light source.
The experiments were conducted in the absence of a filter, in
nitrogen and in air, at light intensities from 30 to 750
mW/cm.sup.2. Three formulations were tested containing HDDA, MDEA,
and ITX, with and without MMI. Representative exotherm peak maxima
and exotherm integration values are shown below in Table 4.
TABLE 4 Data from 1-Second Exposure Photo-DSC Experiments with HDDA
and ITX Formulations (mol % of compound) 0.090% ITX 0.0090% ITX
Light 0.090% ITX 1.0% MDEA 1.01% MDEA In- 0.942% MDEA 0.62% MMI
0.0806% MMI tensity Peak Peak Peak Peak Peak Peak (mW/ Maximum
Integral Maximum Integral Maximum Integral cm.sup.2) (W/g) (J/g)
(W/g) (J/g) (W/g) (J/g) Values in Nitrogen 30 10.25 55.30 31.63
155.97 58.57 272.24 100 25.61 108.70 77.16 400.42 104.95 477.98 300
51.06 216.73 111.13 531.72 122.04 524.88 500 66.52 317.29 117.97
545.81 -- -- 750 93.68 414.60 135.31 564.38 -- -- Values in Air 30
9.29 36.49 2.21 9.34 14.54 55.71 100 23.26 91.58 30.90 132.60 65.20
281.53 300 38.91 170.58 100.60 429.47 111.87 449.55 500 57.56
242.04 115.17 475.92 -- -- 750 -- -- 124.72 510.68 -- --
From this data, it can be clearly observed that in nitrogen, at all
intensities and at both concentrations of MMI, the formulations
containing maleimide perform much better than the HDDA formulation
with only ITX and amine.
Another useful comparison is that between the sensitized
maleimide/ITX/amine initiating system and a typical conventional
alpha-cleavage type photoinitiator. A short set of experiments was
performed using one of the sensitized maleimide containing
formulations from above and an HDDA formulation which contained
2,2-dimethoxy-2-phenylacetophenone (known commercially as BDK and
Irgacure 651). These photo-DSC runs were conducted at 25.degree. C.
in nitrogen, at 100 mW/cm.sup.2 on-sample light intensity, with a
one second exposure time. Photo-DSC exotherm values are given below
in Table 5. The sensitized maleimide-containing formulation gave a
peak maximum on average about 69% of the peak maximum obtained with
the Irgacure 651 formulation. The relative double bond conversion
for the sensitized maleimide initiated formulations was about 79%
of that obtained when the conventional alpha-cleavage
photoinitiator was used. It is interesting to note that there is
0.97 weight percent initiator in the case of the Irgacure 651/HDDA
formulation, but only 0.59 weight percent of initiating system in
the maleimide/ITX/MDEA/HDDA formulation.
TABLE 5 Photo-DSC Exotherm Values Comparing Maleimide/ITX/MDEA to
IC651 in HDDA Formulation (mol Average Exotherm Peak Average
Exotherm Peak % of compound) Maximum (W/g) Integration (J/g)
0.0090% ITX 108.37 489.36 1.01% MDEA 0.0806% MMI 0.86% Irgacure 651
156.70 622.82
Sensitization of Aromatic Maleimides
Experiments were also performed to determine if initiation of
acrylic systems via sensitized aromatic maleimides is possible.
Formulations were prepared using HDDA, ITX, and MDEA with several
aromatic maleimides. The aromatic maleimides used in these
experiments are N-phenylmaleimide (PMI),
N-(2-trifluoromethylphenyl)maleimide (2CF3PMI),
N-(2-t-butylphenyl)maleimide (2tBPMI), and
.alpha.-methyl-N-(2-trifluoromethyl phenyl)maleimide (2CF3PCI).
Photo-DSC experiments were conducted in nitrogen at 25.degree. C.
using a medium pressure mercury lamp fitted with a 365 nm band pass
filter, with an unfiltered on-sample light intensity of 28
mW/cm.sup.2. Exotherm peak maxima are listed below in Table 6. The
data demonstrates that aromatic maleimides can be "sensitized"
(again, though sensitization has not been proven mechanistically)
using ITX in acrylic systems. Also very significant is that the
aromatic maleimides are not required to be "twisted" (as in the
initiation of acrylic systems by direct excitation of the
maleimide), as N-phenyl maleimide appears to have the same
synergistic effect.
TABLE 6 Photo-DSC Peak Maxima for ITX/MDEA/Arylmaleimides in HDDA
Formulation 0.040% 0.040% 0.040% 0.040% 0.040% (mol % of ITX ITX
ITX ITX ITX 1.04% compound) 1.00% 0.976% 0.996% 1.03% MDEA MDEA
MDEA MDEA MDEA 0.325% 0.309% 0.311% 0.313% 2CF3PCI PMI 2CF3PMI
2tBPMI Exotherm 12 34 40 42 46 Peak Maximum (W/g)
In summary, the data reported herein show that a dramatic
synergistic effect occurs when N-aliphatic and N-aromatic
maleimides are used in conjunction with benzophenone/thioxanthone
photoinitiators in the presence of an amine hydrogen atom-donor in
hexanedioldiacrylate. Although not wishing to be bound by any
explanation of the invention, this effect likely occurs through
excitation of the conventional photoinitiator followed by energy
transfer to the maleimide, which then hydrogen-atom abstracts and
initiates free-radical polymerization. Both aliphatic and aromatic
maleimides appear to exhibit the synergism, and the aromatic
maleimides are not required to be "twisted" (the phenyl ring out of
plane with respect to the maleimide ring). Specifically, synergism
leading to enhanced rates of cure and enhanced conversions has been
observed when N-methylmaleimide is used at low concentrations in
conjunction with benzophenone, ITX, LTX, and XPI-115. Enhanced
conversions are also noted when MMI is used in conjunction with
XPI-113 and XPI-133. Similar results have been observed using
N-aromatic maleimides including N-phenylmaleimide,
N-(2-trifluoromethylphenyl)maleimide, N-(2-t-butyl phenyl)
maleimide, and .alpha.-methyl-N-(2-trifluoromethyl
phenyl)maleimide. Under conditions designed to begin to simulate
industrial curing conditions, sensitized maleimide-containing
acrylic formulations were observed to have higher rates of cure and
higher relative conversions in air than the same formulations
without the maleimide in nitrogen.
The foregoing examples are illustrative of the present invention
and are not to be construed as limiting thereof. Many modifications
and other embodiments of the invention will come to mind to one
skilled in the art to which this invention pertains having the
benefit of the teachings presented in the foregoing descriptions
and the associated drawings. Therefore, it is to be understood that
the invention is not to be limited to the specific embodiments
disclosed and that modifications and other embodiments are intended
to be included within the scope of the appended claims. Although
specific terms are employed herein, they are used in a generic and
descriptive sense only and not for purposes of limitation.
* * * * *